Major cold front blows by Friday morning; Saturday high temperatures poised to set records for chilliness
By the time most of you get around Friday morning, the strong cold front will already have blown past Southwest Virginia. It’s wasting no time — it’ll have cleared all of Virginia by Friday evening, and all of Florida by Saturday evening. Behind it, winds will pick up out of the west on Friday, but under sunny skies, temperatures will still make the 60s to low 70s most places. As low pressure develops along the front just off the mid-Atlantic coast later Friday and moves northward along it Saturday, the more intense push of cold air from the northwest will begin, driving temperatures into the 40s (some mid-upper 30s in outlying areas) by Saturday morning. Cold air blowing over the warm Great Lakes, then lifting up the higher terrain of the western side of the Appalachians and condensing, will lead to clouds and some showers Friday night into Saturday. It’s really the same northwest upslope pattern we see intermittently through the winter causing mountain snow squalls — and at the highest elevations, roughly 3,500 feet and up, there could well be snowflakes on Saturday morning, especially along and west of the Interstate 77 corridor and Virginia-West Virginia border. I would not be surprised at all if some locations in western Greenbrier County, W.Va., (think Quinwood) up through the Snowshoe Mountain area got a quick inch or two of slush on grassy areas late Friday into early Saturday. Farther east, and lower in elevation, the surface layer of air is probably going to be too warm to let flakes reach the surface. But there may be enough clouds to really hold back temperatures Saturday — records for coldest Oct. 1 high temperature of 57 at Roanoke and 51 at Blacksburg, both set in1984, could definitely be equalled or beaten. A chilly, breezy night in the 40s will greet the Clemson Tigers to Blacksburg for the game with Virginia Tech on Saturday night — dress like it’s November if you’re going to that game.
Winds may keep frost from forming Sunday morning as tempertures drop into the 30s in much of the area. Winds keep the air mixed, not allowing cold air to simply sink to the surface, and not allowing exposed objects to cool off enough to collect ice crystals. By Monday morning, though, if skies clear and winds still, frost will become more of a possibility, especially in outlying rural valleys into which cold air can sink, and where some readings in the 20s may occur. Roanoke’s official reading may hover in the low 40s on those mornings due to the typical “urban heat island” effect and downsloping winds, but some parts of the metro area will probably be in the mid to upper 30s. Remember that official temperatures are taken at 6 feet above ground, so it can be cold enough for frost at the ground surface under ideal radiational cooling conditions (clear skies, no wind) when it is still a few degrees above freezing at the 6-foot level. In most of Southwest Virginia, it will be a good idea to bring in sensitive plants this weekend.